He evolved a new theory after many years of research.
He has evolved a new theory after many years of research.
The first one has broader use. The second one is a bit more narrow in terms of when you would use it. You may use it when introducing someone, for example at a business meeting or academic job talk:
"He has published in the top academic journals."
In terms of first-person, you'd also use it in such situations as in a job talk:
"I have studied three languages and advanced statistics."
It may express that something is expected to continue. For instance, if I say "I have published in top academic journals," I am likely inferring that I am going to continue to do so. I HAVE done it, and I will continue to do it.
Whereas if someone said about me, "He published in top journals," that would probably be at a funeral or retirement ceremony: it is done, it is over. It will not happen anymore.